• 전기의세계
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• 제18권5호
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• pp.20-25
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• 1969

The development of the frequency convertors using semiconductors devices makes it possible to control the speed of A.C. motors easily. It is now economically feasible to provide them with power at adjustable frequency using silicon-controlled rectifier (or thyristor) inverters. In such a case, in order to operate an induction motor efficiently over a wide speed range, it must be supplied from a variable frequency source of which frequency is adjustable over the speed range of the motor. It is desired to observe the changes in characteristics as primary current, torque-speed of induction motor etc. at any optional frequency. Although the characteristics can be obtained by means of the conventional methods, they require very complicated precedures of calculations. The Current Diagram Method in this paper suggests a new approach to simpler calculations of the characteristics, using the motor constants at reference frequency. The conclusions of this study are summarized as follows: 1) The equations of stator current at adjusted frequency were derived to construct graphical chart and the current circle required for the Current Diagram Method. 2) The radius, center of the current circle and the vector locus, the basis for calculating the characteristics, at any desired frequency could be easily determined with the aid of both the derived graphical chart and current circle at reference frequency. 3) The method was shown to be applicable to the various types of 3-phase induction motors and also dealt with its application to the split-phase, condenser motors.

• Progress in Superconductivity
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• 제3권1호
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• pp.5-12
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• 2001

Our experimental research focuses on manipulating pinning deflects to alter the phase diagram of vortex matter, creating new vortex phases. Vortex matter offers a unique opportunity for creating and studying these novel phase transitions through precise control of thermal, pinning and elastic energies. The vortex melting transition in untwinned YB $a_2$C $u_3$ $O_{7-}$ $\delta$/ crystals is investigated in the presence of disorder induced by particle irradiation. We focus on the low disorder regime, where a glassy state and a lattice state can be realized in the same phase diagram. We follow the evolution of the first order vortex melting transition line into a continuous transition line as disorder is increased by irradiation. The transformation is marked by an upward shift in the lower critical point on the melting line. With columnar deflects induced by heavy ion irradiation, we find a second order Bose glass transition line separating the vortex liquid from a Bose glass below the lower critical point. Furthermore, we find an upper threshold of columnar defect concentration beyond which the lower critical point and the first order melting line disappear together. With point deflect clusters induced by proton irradiation, we find evidence for a continuous thermodynamic transition below the lower critical point..

• 열처리공학회지
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• 제24권5호
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• pp.262-270
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• 2011

Carbide precipitation and dissolution behavior at various temperatures during heat treatment has been studied in STD11 cold working die steel through confocal scanning laser microscopy; dilatometry; and X-ray diffraction analysis. The equilibrium phase diagram and phase fractions with temperature were calculated using a FactSage program. Confocal laser microscopic observation revealed that ${\alpha}$ to ${\gamma}$ transformation temperature is near $800^{\circ}C$; M7C3 carbides melt at $1245^{\circ}C$; and the melting temperature of STD11 is near $1370^{\circ}C$. XRD results indicated that the M23C6 carbides dissolve in the matrix if austenitized at over $1030^{\circ}C$; while the M7C3 carbides remain up to $1200^{\circ}C$ although their amount decreases. The calculated equilibrium phase diagram showed good agreement with experimental results on carbide dissolution and phase transformation temperatures.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.519-524
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• 2018

Carbon/carbon composites (C/C) have been widely studied in the aerospace field because of their excellent thermal shock resistance and specific strength at high temperature. However, they have the problems that is easily oxidized and deteriorated under atmospheric environment. In order to overcome these shortcomings, the CVD coating of ultra-high-temperature ceramics to C/C has become an important technical issue. In this study, thermodynamic calculations were performed to TaC CVD coating on C/C by FactSage 6.2 program. The Ta-C phase diagrams were constructed with the results of thermodynamic calculations in the Ta-C-H-Cl system. Based on the Ta-C phase diagram, the experimental conditions were designed to confirm the deposition of various phases such as TaC single phase, TaC + C and $TaC+Ta_2C$ by varying the composition of Ta/C ratio. The deposited films were found to be in good agreement with the predicted phases.

• 한국실내디자인학회논문집
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• 제17권3호
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• pp.156-164
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• 2008

Through staggering advancements of technology and network as we know them as digital revolution, we have established a foundation of space in which we can express reality by eliminating the boundaries between expression, space, and movement. There are many ongoing approaches that aim to overcome the physically-fixed property of space where the mathematical-geometric notion of Voronoi Diagram is one of them. Although the repetitive increment based on self-organization during the process in which space is generated by the Voronoi Diagram forms a pattern and focuses on the formation, its pattern is not restricted to a single method of expression but evolves over self-control. The result of having analyzed spaces generated by the Voronoi Diagram in this study can be summarized as follows. First, the Voronoi computation method with self-organization property creates multiple levels, increments, and evolves through feedbacks among changes with the slightest order and in the absence of control. Secondly, after forming a pattern through such feedbacks comes the differentiation phase due to the presence of different properties. Thirdly, a space that has gone through the generation process retransforms through active interaction between changes and it obtains ambiguous boundaries and a repetitive pattern. This leads to an evolution of space through repetitive increments based on self-organization. Such flexible space creation is supported by various digital technologies where we believe a converging application of these studies, sciences, engineering concepts, and space design is and effective and new method in terms of space creation.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
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• pp.58-62
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• 2001

본 논문에서는 IMT-2000 통신방식 중 cdma-2000 방식의 시스템을 이용하여 이동통신 단말기 RF System에 미치는 위상 잡음의 영향성을 분석하였다. cdma-2000의 표준안인 TIA/EIA에서 권고한 IS-98-C 를 기초로 하여 위상 잡음 특성의 요구 조건을 유도하였다. 현재 상용화 된 부품을 이용하여 RF 시스템을 설계하여 위상 잡음 특성을 분석하였고 시스템에 가장 큰 영향을 미치는 oscillator의 위상 잡음의 양을 변화시켜 시스템에 미치는 영향을 Constellation Diagram과 Eye Diagram으로 제시 하였다.

• 대한화장품학회지
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• 제18권1호
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• pp.132-149
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• 1992

이 논문은 외관, 안정도, 얇고 균일하게 끈적이지 않는 Film 형성 등의 우수한 특징을 갖고 있기 때문에 Cosmetic preparations의 여러 방면에 응용하고 있는 Microemulsion gel에 관한 것이다. 우리의 연구는 Microemulsion의 Clarifying agent 또는 Coupling agent로 이용되고 있는 Polyol류가 Microemulsion에 미치는 영향을 해명함으로써, Consistency, Stability, Clarity, Pick-up from a container등이 우수한 최적의 Microemulsion gel의 형성 조건을 확립하여 Cosmetic preparations에 응용할 수 있도록 하는 것이다. 연구한 System은 De-ionized water, Oil로는 Polar한 Ester oil, Emulsifying agent는 Nonionic syrfactant, Coupling agent는 Polyol로 구성하였으며, Three component phase diagram과 Tetrahedral phase diagram을 이용하여, Polyol의 비율에 따라 Microemulsion gel의 투명 영역, Consistency, 충격에 의한 Resonance 효과, Pick-up from a container등의 변화를 고찰하였다. 연구결과 구성 성분 중 De-ionized water의 Coupling agent의 비율변화에 의한 영향이 가장 크게 나타났으며, Coupling agent로 사용된 Glycerine의 물에 대한 비율이 63-75%일 때 최적 Microemulsion gel 형성 영역이 가장 넓게 나타났다. 특히 Polyol의 비율을 적절히 선택함으로써, 최근 관심이 모아지고 있는 최소의 유화제량으로 최대의 유상량을 함유한 Microemulsion gel을 얻는데 기여할 수 있을 것으로 생각된다.

• 한국주조공학회지
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• 제15권2호
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• pp.184-193
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• 1995

Effects of process parameters during thixocasting, such as solid volume fraction, mold temperature and extrusion ratio, on the mold filling behaviour and fluidity of Mg alloy(AZ91D) have been investigated. The semi-solid ingot held for 60 minutes at the semi-solid temperature range did not contain the equilibrium volume fraction of solid as expected from the phase diagram. Therefore, in order to obtain the desired solid fractions, and to suppress the exaggerated grain growth during heating, it was required to heat the ingot rapidly up to the temperature $10^{\circ}C$ higher than the semi-solid temperature suggested from the phase diagram for a specific volume fraction of solid. The experimental results show that mold filling behaviour and fluidity can be improved with the use of the higher mold temperature and the lower volume fraction of solid, but remain nearly unaffected by the change of extrusion ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.966-973
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• 2011

Power distribution onboard vessel is typically configured as ungrounded system due to the ability to continuously supply electric power even when an earth fault occurs. The impedance connections between 3 phase power lines and hull cause the line-to-hull voltages to become unstable and increased in case the impedances are unbalanced, bringing the situation susceptible to electric shock and deterioration of insulation material. Also the line-to-hull voltage can reach to a certain maximum value in the steady state depending on the distributed capacitances and grounding resistances between lines and hull. This study suggests how to find and calculate the maximum line-to-hull voltage in view of magnitude and phase angle based on the vector diagram.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.227-250
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• 1999

The reproducibility of successive growth of Bi12TiO20(BTO) single crystals using a top-seeded solution growth (TSSG) pulling method was evaluated by measuring the lattice constants and their standard deviations. A substantial phase diagram in the region close to the stoichiometric BTO was established experimentally for this purpose, and the existence of a retrograde solid solution close to a BTO was clarified. It was emphasize that a starting solution, with a 10.0~10.1 mol% TiO2 concentration, results in large single crystals with a highly homogeneous lattice constant of within $\pm$1x10-4$\AA$, when the solidified fraction of the grown crystal is less than about 45%. A wavelength dispersion of refractive index was measured for the first time, an it was verified that the refractive index of BTO is larger than that of BSO(Bi12TiO20), allowing the voltage sensitivity of EOS higher than the case with BSO as a probe head.